nitrate

When many of the Group I nitrates are heating, the nitrates would be decomposed to give corresponding nitrites. Therefore, the residues are metal nitrites.
For example, 2NaNO3(s) → 2NaNO2(s) + O2(g)

Nitrites are unstable, which reacts with dilute strong acid (e.g. dilute HCl) at room temperature to give nitrogen dioxide gas and nitrogen monoxide gas.
For example, 2HCl(aq) + 2NaNO2(s) → 2NaCl(aq) + H2O(l) + NO2(g) + NO(f)
Nitrogen dioxide is a brown gas, and nitrogen monoxide is a colourless gas which reacts with oxygen at room temperature to give brown nitrogen dioxide gas.
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2009-01-18 23:24:56 補充：
In the second equation, NO(f) should be NO(g).